The invention relates to a coupling device between a workpiece support or a tool support, such as for example a tool system module, for example in the form of a basic tool holding fixture, and an appurtenant handling device, such as for example a machine tool, for example in the configuration of a drilling machine, a lathe, or a milling machine. The coupling device here is to be suitable for stationary and for mobile, such as for example turning workpiece supports or tool supports, such as for example tool system modules.
In the course of the recent technical development up to automated machining centers, the need arises for tool systems, constructed module-like, that must be changeable with the least possible time expended. A series of coupling devices between individual tool system modules have already been developed and suggested that are suitable for stationary and also for turning tools. It has also been attempted to transfer these modular couplings to interfaces between machine tools and tool system modules. But in doing so it has been shown that it is difficult to configure the coupling device in such a way that it equally meets the requirements for stability, position accuracy, lubricant supply of the tool and the capacity to automate the tool change.
Thus, just from the journal "Moderne Fertigung" (Modern Production), November 1986 issue, a coupling device is disclosed between a tool system module and a machine tool in which a mounting is provided on the machine tool side for an extension of the tool system module and a clamping device is provided for generating an engaging pressure between end faces of the parts to be coupled. The clamping device includes an operating rod by which a key mechanism is actuated so that clamping elements in one part to be coupled are pressed radially outward to engage suitably configured recesses on the other part. Thus, a cone connected to the operating rod of the clamping device presses two clamping bodies that are offset diametrically to each other radially outward into suitably shaped recesses of screws that are screwed radially from the exterior into the spindle mounting. The recesses in the screws are configured cone-shaped just like the areas of the clamping bodies that engage in it, and a certain axis offset between the cone of the screw recess and the cone of the clamping body is provided, so that during a radial outward pressing of the clamping bodies an axially-oriented engagement pressure force is generated between the parts to be coupled. The bracing occurs here by relatively large radial end faces, by which a relatively high rigidity of the system results. In any case, these end faces cannot be used for the entire transmission of compressive force, since catch pins must be provided perpendicular to these end faces which provide for an indexing of the tool system module relative to the machine tool or for carrying along the tool system module through the coupling part on the machine tool side such as, i.e., the spindle. To face the problem of attaching a relatively cool tool system module to an already prewarmed coupling part on the machine tool side unconstrained, it is advantageous if the tool system module exhibits a engagement extension and the coupling part on the machine tool side exhibits a mounting provided for this. But in the known case this advantage must be paid for with the drawback that the tool system module must be equipped with a relatively complex mechanism that incorporates the key mechanism, an operating rod and both clamping bodies.
To avoid this relatively great expense, it has already been suggested that this known coupling system be kinematically reversed, i.e., to place the clamping elements together with the operating rod and the key mechanism on the machine tool side. But this leads, in the known case, to the fact that now a centering pin must be attached to the coupling device on the part on the machine tool side. However, by doing this, on the tool system module side an inner area must be produced to precision, which leads to relatively high costs. Further, this system reversal means that when adding a tool system module that has lower temperature than, for example, the already prewarmed machine tool spindle, matching problems can appear, and it must be taken into consideration that for reasons of positioning accuracy, relatively narrow tolerances must be provided.
Further, it has been shown that the rigidity of the interface between tool and machine tool is limited by the fact that the bending moment of resistance of the coupling device in the area of the interface is defined only in the plane that contains the axes of the clamping bodies and the screws. With rotating loads this means that the coupling device is not effectively in a position to counteract the formation of tool vibrations.
Thus the object of the invention is to provide a coupling device of the type described, but which meets the requirements to an improved degree regarding position accuracy of the workpiece support or tool support, such as, e.g., of the tool system module, rigidity of the connection, capacity of the workpiece or tool change to be automated, and flexibility with regard to fields of application and economy. This object is achieved by providing clamping elements that are constructed of at least three claw-type clamps placed peripherally equidistant from one another and essentially parallel to an extension of the tool system module and which is pivoted with a claw section, which is in a coupled state radially inside the extension, into a groovelike recess of the extension.
According to the invention, by providing a clamplike bracing between the parts to be coupled, the flux of force between the coupling parts is improved, i.e., it is kept as even as possible over the periphery of the interface between the tool system module and the machine tool. By homogeneous distribution of force over the periphery, in combination with the configuration according to the invention of the claw-type clamps in the form of essentially axially aligned clamplike elements, the construction space needed in the radial direction for the claw-type clamps becomes very small, due to which the possibility arises that the end faces that are in junction with each other of the parts to be coupled can be constructed very large. Because, further, with the configuration according to the invention of the coupling device, no mobile part is necessary near the axis, there results a compatibility with most varied tool systems, for example also those in which a modular coupling with axial attachment screws is constructed. In doing so, it is still made certain that temperature-related difficulties during change of the tool system module are excluded right from the basic concept, since the optionally colder tool system module engages with an extension in a mounting. The relatively more expensive matching inner area here is formed in the area of the part on the machine tool side, thus reducing the costs of the tool system module. This results in the particular advantage that there are no more mobile parts in the tool system module, by which the production costs can be reduced considerably.
The advantages described above result for every kind of a coupling between a workpiece support or tool support and a handling device, which for example can be made up of a workpiece changing system.
The design of the coupling device according to the invention has advantages especially when it is used in the area of the interface between a machine tool spindle and a basic tool holding fixture. In this case, an extremely simple spindle structure results, since all parts can be configured dynamically balanced. An additional advantage here can be seen in the fact that spindles of machine tools commercially available can be retrofitted with low expense with the coupling system according to the invention, and the connecting rod already provided in the spindles can continue to be used and only a supplementary spindle flange that carries the claw-type clamps must be constructed. In doing so, the lifting path to release the coupling device is still considerably reduced relative to a standard coupling system with a steep angle taper. Since, on the tool system module side only an end face and a centering extension must be constructed, it is also possible to provide structurally identical, standardized gripper slots for an automatic tool change, by which additional economic advantages result and the advantages of cylinder fit with regard to the positioning accuracy is still retained.
The dynamically balanced configuration of the coupling device further offers, in an advantageous way, the possibility of transmitting the engagement pressure without transverse force and in this way of raising the positioning accuracy and ultimately also the stability of the tool. Under the action of the key mechanism, the clamplike claw-type clamps conform extremely uniformly to a flank in the groovelike recess of the centering extension, and by suitable configuration of the areas of the key mechanism that are in engagement, an introduction of the binding force that is as loss-free as possible can occur. Here, it is further an advantage that the small elastic deformation of the centering extension caused by the pressing outward of the claw-type clamps has the tendency to form the fit between spindle and tool system module more exactly, i.e., to improve it.
The generation of the axial engagement pressure without transverse force is additionally improved by providing a longitudinal bore in the operating rod for supplying lubricant therein. In this way a floating support of the operating rod is provided, by which the thrust cone, upon introduction of the force, undergoes an automatic centering radially within the claw-type clamps. The claw-type clamps themselves are braced, with their end facing away from the claw section, in a radially selected position in the mounting, so that a mechanism is provided that works unconstrained and with which the engagement pressure can be generated over the periphery extremely is provided uniformly.
When the thrust cone is placed radially inside the claw sections, there results an immediate introduction of the cone force onto the claw sections, and a power transmission ratio occurs by the key areas of the key mechanism. A further power transmission ratio step is generated according to the invention by the pivoting of the claw sections into the groovelike recess in the centering extension, so that very high axial clamping forces can be applied. The coupling device according to the invention is accordingly suitable for use at interfaces of nearly all types of machine tools.
Basically it is possible to secure the claw-type clamps at any point in the centering mounting of a spindle in such a way that, while retaining a predetermined radial position, they can be brought in and out of engagement with the groovelike recess of the centering extension. But especially advantageous is the further development according to which one of the supporting grooves provided for the claw-type clamps is constructed in a catch ring that is placed in the centering mounting.
The advantage achieved by using at least one engaging dog that engages in the front of the centering cylinder in a recess to introduce selectively the forces occurring during torque transmission and thus to keep the engagement end faces between the parts to be coupled undamaged, is also maintained even when the catch ring supports the at least one engaging dog. Further, there results the advantage, from a production engineering viewpoint, that the functional areas provided for the pivoting movement of the claw-type clamps and for the transmission of peripheral force are now formed on a single component and thus can be produced with greater precision with regard to the controlled vane position to one another.
From a production engineering viewpoint, suitably configuring the catch extension of the catch ring is advantageous, since in this way only one axial machining of the part on the machine tool side, for example of the machine tool spindle, must occur.
It has been shown that by the prism-like configuration of the catch extension on the catch ring, very high peripheral forces can be transmitted, and the working diameter of the catch extension can remain relatively limited. For the construction of the catch extension, basically any regular polygon cross section can serve as the basis. But it has been shown that good results can be achieved on the basis of a triangular prism with rounded edges and prime surfaces that are curved convex. In this way there results a non-slip connection in the form of a so-called K-profile, however, the level areas provided there between the edge curves are replaced by convex areas.
The service value of the coupling device according to the invention is also increased by supporting diametrically opposed engaging dogs by the catch ring, the plane of symmetry thereof enclosing an angle of 30.degree. with one of three axial planes passing through the catch extension. With this configuration not only is it achieved that the peripheral forces occurring during torque transmission are symmetrically transmitted, but furthermore the condition is provided so that an indexing of the tool system module relative to the machine tool can occur in increments of 30.degree..
For additional stabilization of the claw-type clamps, the function of fixing the catch ring selectively in the centering mounting can be simultaneously transferred to the guide cylinder, by which the number of components can be reduced.
By providing an elastic ring for an annular slot in the guide cylinder, the condition for the floating support of the operating rod in the area of the key mechanism as mentioned above, by which it becomes possible to implement the automatic centering effect, but in doing so, at the same time the coupling operation is not made more difficult, since the elastic gasket provides for a sufficient advance centering of the coupling parts.
As initially explained above, the configuration of the coupling device according to the invention offers a purely dynamically balanced design that needs no components in the vicinity of the axis. In an advantageous way this offers the possibility of supplying the tool system module, by symmetrical supply channels, with coolant or lubricant for the tool. For this purpose, it is necessary only that the operating rod receives a longitudinal bore for lubricant. This lubricant is then conveyed further inside the thrust cone and is fed by a hollow pin to a coaxial recess in the tool system module.
As an alternative to this it is possible to provide in the thrust cone an axially centered bore, into which a hollow pin fastened in the tool system module can engage as a seal. In this way the lubricant supply can continue to occur without radial deflections, but it is additionally taken care of that the lifting movement during release of the coupling device remains limited to the axial linear dimension of the centering cylinder.
An especially advantageous configuration of the groovelike recess in the centering extension or centering cylinder is one in which the annular slot therein exhibits a V cross section, since this groove can be produced in the perforation process.
The design according to the invention of the coupling device offers the possibility of configuring the functional areas between claw-type clamps, mounting cylinder and centering cylinder so that engagement areas with as large a surface area as possible arise.
If a centering ring which is fastened radially adjustably on a spindle is provided, the concentricity can additionally be made adjustable, by which the positioning accuracy of the tool system module can be further raised.
By the configuration of the claw sections of a key flank slanting on the outside down to the tool system module, the design of the coupling device can be additionally simplified. The key flank slanting down to the tool system module has the effect that the centering cylinder, upon insertion into the machine tool recess, pushes the claw sections radially inward.
An additional advantage of the coupling device described above can again be seen in the fact that it is possible, with a single interface, to carry out diameter reductions, i.e., transitions from a relatively large spindle diameter to a relatively small diameter of the tool system module, without increasing the total axial length. For this purpose, it is necessary only to insert into the centering mounting a suitably shaped reducing ring and claw-type clamps which are correspondingly offset radially inward and which can then be brought into functional engagement with an optionally somewhat modified thrust cone.
It has been shown that especially good results can be achieved with six claw-type clamps.
In the suggestion for the coupling device described above, a homogeneous force distribution over the periphery and an exact positioning of the parts to be coupled to one another is dependent on the state of the functional areas of the parts to be coupled that can be brought into matching engagement with one another. The need thus arises to keep these functional areas used in the coupling device clean, even under rough conditions, i.e., in use with the greatest cutting power and even with unfavorable formation of a cutting, and to keep the device engineering expense necessary for this as small as possible. The functional areas of the parts of the coupling device that can be brought into engagement are, in the released state of the coupling, preferably cleansed continuously with compressed air so that dirt, grinding dust and the like cannot cling to the matching areas. Damages to the matching areas can thus effectively be ruled out so that the lifetime of the coupling device is additionally increased.
With the dynamically balanced design of the coupling device of this invention, there results a very simple supply of compressed air to the sluice system which cleanses effectively the end face engagement between the tool system module and the spindle. The compressed air sluices in the radial ring area segments assure that when the tool system module approaches the area of the matching areas, a constantly, increasingly accelerated compressed air flow is generated between the matching areas to be moved on each other, by which even the finest grinding dust is reliably removed from the matching area. In doing so, the grooves between the radial ring area segments additionally act as elutriation chambers, so that keeping these matching areas clean is additionally simplified.
According to the present invention, the function of selectively fixing the catch ring in the centering mounting is simultaneously conferred upon the guide cylinder, by which the number of components can be reduced. By the configuration according to the invention of the annulus that can be suppled with compressed air, the available compressed air is fed with low losses to the important points that are to be kept clean or to be cleansed. This further development is advantageous especially if longitudinal grooves in the catch ring run out radially and merge into an annular gap which opens to a cylindrical matching area and rotates, since in this way the compressed air flowing through the branch channels can be kept, from the viewpoint of great mass throughout, so great that not only the end face but also the cylindrical matching innder area can be rinsed or cleansed.
According to another configuration of the guide cylinder according to this invention, the condition for the floating support of the operating rod in the area of the key mechanism is afforded, by which the automatic centering effect can be achieved, but in doing so simultaneously the coupling operation itself is not made more difficult, since the elastic gasket takes care of a sufficient advance centering of the coupling parts.
If a centering ring is provided with compressed air sluices, the concentricity can in addition be made adjustable, by which the positioning accuracy of the tool system module can be further raised. Construction of the compressed air sluices in the centering ring results in a very cost effective preparation of the sluice system, since the compressed air sluices can be accommodated in a separate component. This results in the additional advantage that by using the centering ring which, for its statically determined mounting in the spindle is in engagement with the spindle only at an end face and at a cylindrical matching area, an annulus on the back side of the centering ring necessarily arises by which the compressed air can be uniformly distributed to the individual sluices. An annular gap to clean the cylindrical matching area between spindle and tool system module can be provided simply in this way in that suitable matching of the diameter of the catch ring and the centering ring occurs.
Further advantageous configurations of the invention are the object of the remaining subclaims.